The present invention is directed to bicycles and, more particularly, to various features of an electrically controlled bicycle transmission.
Bicycle transmissions usually comprise either internally mounted transmissions or externally mounted transmissions. Internally mounted transmissions usually are built into the hub of the rear wheel, and externally mounted transmissions usually have a derailleur for switching a chain among a plurality of sprockets. A shift control device mounted to the bicycle frame and connected to the transmission by a shift control cable usually controls both types of transmissions.
Recently, automatic shift control devices have been developed to operate the bicycle transmission. Such automatic shift control devices usually operate the bicycle transmission to select a high gear to accommodate high speed traveling and to select a low gear to accommodate low speed travel. The automatic shift control device usually has an electric motor for operating the shift control cable, a control part containing a microprocessor or the like that controls the electric motor, and a wheel speed sensor that outputs wheel speed signals. The wheel speed sensor typically includes a frame-mounted sensor that detects the passage of a magnet attached to the bicycle wheel, and the microprocessor outputs control signals for controlling the motor to switch gears in response to the wheel speed signals.
It is sometimes desirable to change gears manually in an automatic shift control device, and sometimes a manual switch or the like is operatively coupled to the microprocessor for that purpose. The manual switch typically generates an interrupt signal to the microprocessor, and the microprocessor executes different program routines to accomplish the manual gear change. Of course, this requires a separate port in the microprocessor and appropriate programming to accommodate automatic and manual modes of operation, which increases the complexity of the device. Furthermore, it may not be possible to add a manual gear changing mode at all to an apparatus that has been provided with only an automatic gear changing mode, and with a conventional system it may be necessary to make large changes to the hardware configuration and the control program of the microprocessor, thus making manual gear changing operations impracticable.
The present invention is directed to various features of an electrically controlled bicycle transmission. In one inventive feature, a shift control device is provided for a bicycle that uses shift control signals from a signal provider to operate an automatic shifting mechanism of a bicycle transmission, wherein the shift control signals correspond to a traveling condition. The shift control device comprises an override shift command unit for providing an override shift command, and a simulation unit operatively coupled to the override shift command unit for providing simulated shift control signals in response to the override shift command.
In another inventive feature, a shift control device is provided for operating an automatic shifting mechanism of a bicycle transmission. The shift control device comprises a signal provider that provides shift control signals corresponding to a traveling condition; an override shift command unit for providing an override shift command; a simulation unit operatively coupled to the signal provider and to the override shift command unit for providing simulated shift control signals in response to the override shift command; and a gear change unit that outputs signals for operating the bicycle transmission in response to the shift control signals and the simulated shift control signals. Additional inventive features will become apparent from the description below, and such features may be combined with the above features to provide additional benefits.